A page from the Flowery Triod (Triod' cvetnaja) from about 1491, one of the oldest printed Byzantine-Slavonic books, National Library of Poland.

The language was standardized for the mission of the two apostles to Great Moravia (the territory of today's western Slovakia and Czech Republic; see Glagolitic alphabet for details). For that purpose, Cyril and his brother Methodius started to translate religious literature to Old Church Slavonic, allegedly based on the Slavic dialects spoken in the hinterland of their hometown, Thessaloniki,[7] in today's Greece.

As part of the preparation for the mission, in 862/863, the Glagolitic alphabet was created and the most important prayers and liturgical books, including the Aprakos Evangeliar (a Gospel Booklectionary containing only feast-day and Sunday readings), the Psalter, and Acts of the Apostles, were translated. (The Gospels were also translated early, but it is unclear whether Sts. Cyril or Methodius had a hand in this.)

The language and the alphabet were taught at the Great Moravian Academy (Slovak: Veľkomoravské učilište) and were used for government and religious documents and books between 863 and 885. The texts written during this phase contain characteristics of the Slavic vernaculars in Great Moravia.

In 885, the use of Old Church Slavonic in Great Moravia was prohibited by Pope Stephen V in favour of Latin.[8]

The texts written during this era exhibit certain linguistic features of the vernaculars of the First Bulgarian Empire. Old Church Slavonic spread to other South-Eastern, Central, and Eastern European Slavic territories, most notably Croatia, Serbia, Bohemia, Lesser Poland, and principalities of the Kievan Rus' while retaining characteristically South Slavic linguistic features.

Later texts written in each of those territories then began to take on characteristics of the local Slavic vernaculars and, by the mid-11th century, Old Church Slavonic had diversified into a number of regional varieties (known as recensions). These local varieties are collectively known as the Church Slavonic language.[12]

Church Slavonic maintained a prestigious status, particularly in Russia, for many centuries – among Slavs in the East it had a status analogous to that of Latin in Western Europe, but had the advantage of being substantially less divergent from the vernacular tongues of average parishioners.

For Old Church Slavonic, the following segments are reconstructible.[14] A few sounds are given in Slavic transliterated form rather than in IPA, as the exact realisation is uncertain and often differs depending on the area that a text originated from.

The letter щ denoted different sounds in different dialects and is not shown in the table. In Bulgaria, it represented the sequence /ʃt/, and it is normally transliterated as št for that reason. Farther west and north, it was probably /c(ː)/ or /tɕ/ like in modern Macedonian, Torlakian and Serbian/Croatian[citation needed].

/dz/ appears mostly in early texts, becoming /z/ later on.

The distinction between l, n and r, on one hand, and palatal l', n' and r', on the other, is not always indicated in writing. When it is, it is shown by a palatization diacritic over the letter: л҄ н҄ р҄.

The pronunciation of yat (ѣ/ě) differed by area. In Bulgaria it was a relatively open vowel, commonly reconstructed as /æ/, but further north its pronunciation was more closed and it eventually became a diphthong /je/ (e.g. in modern standard Croatian) or even /i/ in many areas (e.g. in Chakavian Croatian, ShtokavianIkavian Croatian dialects or Ukrainian) or /e/ (modern standard Serbian).

The yer (ъ) and (ь) vowels ĭ and ŭ are often called "ultrashort" and were lower, more centralised and shorter than their counterparts i and y/u. They disappeared in most positions in the word, already sporadically in the earliest texts but more frequently later on. They also tended to merge with other vowels, particularly ĭ with e and ŭ with o, but differently in different areas.

The exact articulation of the nasal vowels is unclear because different areas tend to merge them with different vowels. ę /ɛ̃/ is occasionally seen to merge with e or ě in South Slavic, but becomes ja early on in East Slavic. ǫ /ɔ̃/ generally merges with u or o, but in Bulgaria, ǫ was apparently unrounded and eventually merged with ŭ.

Several notable constraints on the distribution of the phonemes can be identified, mostly resulting from the tendencies occurring within the Common Slavic period, such as intrasyllabic synharmony and the law of open syllables. For consonant and vowel clusters and sequences of a consonant and a vowel, the following constraints can be ascertained:[15]

Phonetically palatalized consonants do not occur before certain back vowels

The back vowels /y/ and /ъ/ as well as front vowels other than /i/ do not occur word-initially: the two back vowels take prothetic /v/ and the front vowels prothetic /j/. Initial /a/ may take either prothetic consonant or none at all.

Vowel sequences are attested in only one lexeme (paǫčina 'spider's web') and in the suffixes /aa/ and /ěa/ of the imperfect

As a result of the first and the second Slavic palatalizations, velars alternate with dentals and palatals. In addition, as a result of a process usually termed iotation (or iodization), velars and dentals alternate with palatals in various inflected forms and in word formation.

Alternations in velar consonants

original

/k/

/g/

/x/

/sk/

/zg/

/sx/

first palatalization and iotation

/č/

/ž/

/š/

/št/

/žd/

/š/

second palatalization

/c/

/dz/

/s/

/sc/, /st/

/zd/

/sc/

Alternations in other consonants

original

/b/

/p/

/sp/

/d/

/zd/

/t/

/st/

/z/

/s/

/l/

/sl/

/m/

/n/

/sn/

/zn/

/r/

/tr/

/dr/

iotation

/bl'/

/pl'/

/žd/

/žd/

/št/

/št/

/ž/

/š/

/l'/

/šl'/

/ml'/

/n'/

/šn'/

/žn'/

/r'/

/štr'/

/ždr'/

In some forms the alternations of /c/ with /č/ and of /dz/ with /ž/ occur, in which the corresponding velar is missing. The dental alternants of velars occur regularly before /ě/ and /i/ in the declension and in the imperative, and somewhat less regularly in various forms after /i/, /ę/, /ь/ and /rь/.[16] The palatal alternants of velars occur before front vowels in all other environments, where dental alternants do not occur, as well as in various places in inflection and word formation described below.[17]

Vowel:∅ alternations sometimes occurred as a result of sporadic loss of weak yer, which later occurred in almost all Slavic dialects. The phonetic value of the corresponding vocalized strong jer is dialect-specific.

As an ancient Indo-European language, OCS has a highly inflective morphology. Inflected forms are divided in two groups, nominals and verbs. Nominals are further divided into nouns, adjectives and pronouns. Numerals inflect either as nouns or pronouns, with 1-4 showing gender agreement as well.

Adjectives are inflected as o/jo-stems (masculine and neuter) and a/ja-stems (feminine), in three genders. They could have short (indefinite) or long (definite) variants, the latter being formed by suffixing to the indefinite form the anaphoric third-person pronoun jь.

Synthetic verbal conjugation is expressed in present, aorist and imperfect tenses while perfect, pluperfect, future and conditional tenses/moods are made by combining auxiliary verbs with participles or synthetic tense forms. Sample conjugation for the verb vesti "to lead" (underlyingly ved-ti) is given in the table below.

Written evidence of Old Church Slavonic survives in a relatively small body of manuscripts, most of them written in First Bulgarian Empire during the late 10th and the early 11th centuries. The language has a Southern Slavic basis with an admixture of Western Slavic features inherited during the mission of Saints Cyril and Methodius to Great Moravia (863–885).

The only well-preserved manuscript of the Moravian recension, the Kiev Folia, is characterised by the replacement of some Southern Slavic phonetic and lexical features with Western Slavic ones. Manuscripts written in the Second Bulgarian Empire (1185-1396) have, on the other hand, few Western Slavic features.

Old Church Slavonic is valuable to historical linguists since it preserves archaic features believed to have once been common to all Slavic languages such as these:

Old Church Slavonic is also likely to have preserved an extremely archaic type of accentuation (probably[citation needed] close to the Chakavian dialect of modern Serbo-Croatian), but unfortunately, no accent marks appear in the written manuscripts.

The Southern Slavic nature of the language is evident from the following variations:

The language was standardized for the first time by the mission of the two apostles to Great Moravia from 863. The manuscripts of the Moravian recension are therefore the earliest dated of the OCS recensions.[clarification needed] The recension takes its name from the Slavic state of Great Moravia which existed in Central Europe during the 9th century on the territory of today's western Slovakia and Czech Republic.

Old Church Slavonic language is developed in the First Bulgarian Empire and was taught in Preslav (Bulgarian capital between 893 and 972), and in Ohrid (Bulgarian capital between 991/997 and 1015).[18][19][20] It did not represent one regional dialect but a generalized form of early eastern South Slavic, which cannot be localized.[21] The existence of two major literary centres in the Empire led in the period from the 9th to the 11th centuries to the emergence of two recensions (otherwise called "redactions"), termed "Bulgarian" and "Macedonian" respectively.[22][23] Some researchers do not differentiate between manuscripts of the two recensions, preferring to group them together in a "Macedo-Bulgarian"[24] or simply "Bulgarian" recension.[25][26] Others, as Horace Lunt, have changed their opinion with time. In the mid-1970s, Lunt held that the differences in the initial OCS were neither great enough nor consistent enough to grant a distinction between a 'Macedonian' recension and a 'Bulgarian' one. A decade later, however, Lunt argued in favour of such a distinction, illustrating his point with paleographic, phonological and other differences.[27] The development of Old Church Slavonic literacy had the effect of preventing the assimilation of the South Slavs into neighboring cultures, which promoted the formation of a distinct Bulgarian identity.[28]

Later use of the language in a number of medieval Slavic polities resulted in the adjustment of Old Church Slavonic to the local vernacular, though a number of Southern Slavic, Moravian or Bulgarian features also survived. Significant later recensions of Old Church Slavonic (referred to as Church Slavonic) in the present time include: Slovene, Croatian, Serbian and Russian. In all cases, denasalization of the yuses occurred; so that only Old Church Slavonic, modern Polish and some isolated Bulgarian dialects retained the old Slavonic nasal vowels.

The Serbian recension[39] was written mostly in Cyrillic, but also in the Glagolitic alphabet (depending on region); by the 12th century the Serbs used exclusively the Cyrillic alphabet (and Latin script in coastal areas). The 1186 Miroslav Gospels belong to the Serbian recension. They feature the following linguistic characteristics:

The line between OCS and post-OCS manuscripts is arbitrary, and terminology varies. The common term "Middle Bulgarian" is usually contrasted to "Old Bulgarian" (an alternative name for Old Church Slavonic), and loosely used for manuscripts whose language demonstrates a broad spectrum of regional and temporal dialect features after the 11th century.[41]

PSl. weak-positionedyers *ъ and *ь in merged, probably representing some schwa-like sound, and only one of the letters was used (usually 'ъ'). Evident in earliest documents like Baška tablet.

PSl. strong-positionedyers *ъ and *ь were vocalized into a in most Štokavian and Čakavian speeches, e.g. Cr. pas : OCS pьsъ ("dog")

PSl. hard and soft syllabic liquids *r and r′ retained syllabicity and were written as simply r, as opposed to OCS sequences of mostly rь and rъ, e.g. krstъ and trgъ as opposed to OCS krьstъ and trъgъ ("cross", "market")

The core corpus of Old Church Slavonic manuscripts is usually referred to as canon. Manuscripts must satisfy certain linguistic, chronological and cultural criteria to be incorporated into the canon: they must not significantly depart from the language and tradition of Sts. Cyril and Methodius, usually known as the Cyrillo-Methodian tradition.

For example, the Freising Fragments, dating from the 10th century, show some linguistic and cultural traits of Old Church Slavonic, but they are usually not included in the canon, as some of the phonological features of the writings appear to belong to certain Pannonian Slavic dialect of the period. Similarly, the Ostromir Gospels exhibits dialectal features that classify it as East Slavic, rather than South Slavic so it is not included in the canon either. On the other hand, the Kiev Missal is included in the canon even though it manifests some West Slavic features and contains Western liturgy because of the Bulgarian linguistic layer and connection to the Moravian mission.

Manuscripts are usually classified in two groups, depending on the alphabet used, Cyrillic or Glagolitic. With the exception of the Kiev Missal and Glagolita Clozianus, which exhibit West Slavic and Croatian features respectively, all Glagolitic texts are assumed to be of the Macedonian recension:

Our father
Thou Who art in heaven.
May hallowed be Thy Name
may come Thy empire
may become Thy will
as in heaven, also on Earth.
Our supersubstantial bread
give us this day
and release us of our debts
as we also release
our debtors,
and do not lead us to temptation
but free us from the evil.
As Thine is the empire
and the power and the glory unto the ages of ages.
Amen.

The history of Old Church Slavonic writing includes a northern tradition begun by the mission to Great Moravia, including a short mission in the Balaton principality, and a Bulgarian tradition begun by some of the missionaries who relocated to Bulgaria after the expulsion from Great Moravia.

Old Church Slavonic's first writings, translations of Christian liturgical and Biblical texts, were produced by Byzantine missionaries Saint Cyril and Saint Methodius, mostly during their mission to Great Moravia.

The name of the language in Old Church Slavonic texts was simply Slavic (словѣ́ньскъ ѩꙁꙑ́къ, slověnĭskŭ językŭ),[44] derived from the word for Slavs (словѣ́нє, slověne), the self-designation of the compilers of the texts. This name is preserved in the modern names of the Slovak and Slovene languages. The language is sometimes called Old Slavic, which may be confused with the distinct Proto-Slavic language. Different strains of nationalists have tried to 'claim' Old Church Slavonic; thus OCS has also been variously called "Old Bulgarian", "Old Croatian", "Old Macedonian", or "Old Serbian", or even "Old Slovak", "Old Slovenian".[45] The commonly accepted terms in modern English-language Slavic studies are Old Church Slavonic and Old Church Slavic.

^Waldman & Mason 2006, p. 752: "There is disagreement as to whether Cyril and his brother Methodius were Greek or Slavic, but they knew the Slavic dialect spoken in Macedonia, adjacent to Thessalonika."

^After the Slavs invaded it.Curta 2006, p. 214: "At the emperor's request, Constantine and his brother started the translation of religious texts into Old Church Slavonic, a literary language most likely based on the Macedonian dialect allegedly used in the hinterland of their home-town, Thessalonica."

^Stolz, Titunik & Doležel 1984, p. 111: "Specific phonological and lexical differences led Jagić (and many others after him, notably Vaillant) to distinguish carefully between the Western (or Macedonian) OCS of the glagolithic manuscripts and the Eastern (or Bulgarian) OCS of the Suprasliensis…"